<template>
   <el-color-picker
      v-model="theme"
      :predefine="[
         '#409EFF',
         '#1890ff',
         '#304156',
         '#212121',
         '#11a983',
         '#13c2c2',
         '#6959CD',
         '#f5222d'
      ]"
      class="theme-picker"
      popper-class="theme-picker-dropdown"
   />
</template>

<script>
const version = require('element-ui/package.json').version // element-ui version from node_modules
const ORIGINAL_THEME = '#409EFF' // default color
export default {
   data() {
      return {
         chalk: '', // content of theme-chalk css
         theme: ''
      }
   },
   computed: {
      defaultTheme() {
         return this.$store.state.settings.theme
      }
   },
   watch: {
      defaultTheme: {
         handler: function(val, oldVal) {
            this.theme = val
         },
         immediate: true
      },
      async theme(val) {
         const oldVal = this.chalk ? this.theme : ORIGINAL_THEME
         if (typeof val !== 'string') return
         const themeCluster = this.getThemeCluster(val.replace('#', ''))
         const originalCluster = this.getThemeCluster(
            oldVal.replace('#', '')
         )
         console.log(themeCluster, originalCluster)
         const $message = this.$message({
            message: '  Compiling the theme',
            customClass: 'theme-message',
            type: 'success',
            duration: 0,
            iconClass: 'el-icon-loading'
         })
         const getHandler = (variable, id) => {
            return () => {
               const originalCluster = this.getThemeCluster(
                  ORIGINAL_THEME.replace('#', '')
               )
               const newStyle = this.updateStyle(
                  this[variable],
                  originalCluster,
                  themeCluster
               )
               let styleTag = document.getElementById(id)
               if (!styleTag) {
                  styleTag = document.createElement('style')
                  styleTag.setAttribute('id', id)
                  document.head.appendChild(styleTag)
               }
               styleTag.innerText = newStyle
            }
         }
         if (!this.chalk) {
            const url = `https://unpkg.com/element-ui@${version}/lib/theme-chalk/index.css`
            await this.getCSSString(url, 'chalk')
         }
         const chalkHandler = getHandler('chalk', 'chalk-style')
         chalkHandler()
         const styles = [].slice
            .call(document.querySelectorAll('style'))
            .filter(style => {
               const text = style.innerText
               return (
                  new RegExp(oldVal, 'i').test(text) &&
                  !/Chalk Variables/.test(text)
               )
            })
         styles.forEach(style => {
            const { innerText } = style
            if (typeof innerText !== 'string') return
            style.innerText = this.updateStyle(
               innerText,
               originalCluster,
               themeCluster
            )
         })
         this.$emit('change', val)
         $message.close()
      }
   },
   methods: {
      updateStyle(style, oldCluster, newCluster) {
         let newStyle = style
         oldCluster.forEach((color, index) => {
            newStyle = newStyle.replace(
               new RegExp(color, 'ig'),
               newCluster[index]
            )
         })
         return newStyle
      },
      getCSSString(url, variable) {
         return new Promise(resolve => {
            const xhr = new XMLHttpRequest()
            xhr.onreadystatechange = () => {
               if (xhr.readyState === 4 && xhr.status === 200) {
                  this[variable] = xhr.responseText.replace(
                     /@font-face{[^}]+}/,
                     ''
                  )
                  resolve()
               }
            }
            xhr.open('GET', url)
            xhr.send()
         })
      },
      getThemeCluster(theme) {
         const tintColor = (color, tint) => {
            let red = parseInt(color.slice(0, 2), 16)
            let green = parseInt(color.slice(2, 4), 16)
            let blue = parseInt(color.slice(4, 6), 16)
            if (tint === 0) {
               // when primary color is in its rgb space
               return [red, green, blue].join(',')
            } else {
               red += Math.round(tint * (255 - red))
               green += Math.round(tint * (255 - green))
               blue += Math.round(tint * (255 - blue))
               red = red.toString(16)
               green = green.toString(16)
               blue = blue.toString(16)
               return `#${red}${green}${blue}`
            }
         }
         const shadeColor = (color, shade) => {
            let red = parseInt(color.slice(0, 2), 16)
            let green = parseInt(color.slice(2, 4), 16)
            let blue = parseInt(color.slice(4, 6), 16)
            red = Math.round((1 - shade) * red)
            green = Math.round((1 - shade) * green)
            blue = Math.round((1 - shade) * blue)
            red = red.toString(16)
            green = green.toString(16)
            blue = blue.toString(16)
            return `#${red}${green}${blue}`
         }
         const clusters = [theme]
         for (let i = 0; i <= 9; i++) {
            clusters.push(tintColor(theme, Number((i / 10).toFixed(2))))
         }
         clusters.push(shadeColor(theme, 0.1))
         return clusters
      }
   }
}
</script>

<style>
.theme-message,
.theme-picker-dropdown {
   z-index: 99999 !important;
}
.theme-picker .el-color-picker__trigger {
   height: 26px !important;
   width: 26px !important;
   padding: 2px;
}
.theme-picker-dropdown .el-color-dropdown__link-btn {
   display: none;
}
.el-color-picker {
   height: auto !important;
}
</style>
